Numerical simulations of a summer blocking process in Northeast Asia using two microphysical schemes

The mesoscale model WRF driven by the NCEP/NCAR FNL reanalysis data is used to simulate a blocking process occurred in Northeast Asia during 25 July—3 August 2011. Comparative analysis of numerical experiments with and without ice phase microphysical processes is conducted to discuss the WRF model ability for the simulation of the strength and maintenance time of the blocking process. The results show that the WRF model can well simulate this blocking process. The results using the microphysical scheme with ice phase process show that the simulated blocking intensity and maintenance time are close to observations. The overall blocking pattern with closed circulation, the pressure value at the blocking high center and its location, the strength of the low-pressure trough upstream and downstream of the high pressure center are consistent with actual situation. The simulation using the microphysics scheme without ice-phase process cannot reproduce the closed high pressure contour in the mean geopotential height fields at 500 and 200 hPa. The simulated blocking is weaker in intensity and shorter in duration than observations at 500 hPa, while the opposite is true at 200 hPa.

Further study shows that the differences between the two experiments are mainly caused by different diabatic heating in the blocking area, which is a good indicator of the strength and duration of the blocking. In addition, the microphysical latent heat release near the blocking area also affects the strength and maintenance time of the blocking process.